This invention relates to personal care compositions.
Antiperspirant and deodorant compositions are well known personal care products. The compositions come in a variety of forms and may be formulated, for example, into aerosols, pumps, sprays, liquids, roll-on, lotions, creams, gels, sticks (both hard and soft), etc.
It is known that optically clear antiperspirant and deodorant compositions are desirable for aesthetic reasons. Three techniques generally have been used to provide such optically clear compositions. One technique involves matching the refractive indices of two immiscible phases in an emulsion. A second technique involves solidifying a solution with an optically clear gellant. A third technique involves forming a microemulsion of immiscible components.
It is also known that including volatile silicones in antiperspirant and deodorant composition is desirable because the volatile silicones act as a volatile carriers to provide reduced tackiness, increased glide, and a dry feel during and post application. It is also known that certain silicone polyethers can be used as surfactants to reduce white residue, to increase polar compatibility, and to lubricate.
Volatile silicones have previously been included in optically clear antiperspirant and deodorant compositions. For example, antiperspirant and deodorant compositions including an emulsion having an oil phase and a water phase can be made optically clear by closely matching the refractive indexes of the two phases (the first technique mentioned above). But closely matching the refractive indexes of the two can be tedious and the system is inherently thermodynamically unstable.
In one aspect the invention features an optically clear personal care composition, such as an antiperspirant or deodorant, including water, a volatile silicone, and a silicone polyether that has a molecular weight greater than 1,000 daltons and an HLB greater than 4. Including the silicone polyether in the composition results in the formation of a microemulsion including the water and volatile silicone. The composition is optically clear because of formation of the microemulsion. The invention therefore provides convenient and easy way to provide an optically clear personal care composition including a volatile silicone.
Optically clear, as used herein, means that (1) the composition has a sufficient clarity to allow Font 8 text to be read through a 1 cm layer of the composition at normal light; and/or (2) the composition has an optical clarity better than 100 NTU Nephelometric Turbidity Units) at 21xc2x0 C. measured with an Orbeco-Hellige #965 Direct-Reading Turbidimeter. Preferred compositions have a sufficient clarity to allow the Font 8 text to be read through a 2 cm layer of the composition, and more preferred compositions may have a sufficient clarity to allow the Font 8 text to be read through a 5 cm layer of the composition. Preferred compositions also may have an optical clarity better than 70 NTU at 21xc2x0 C., and more preferably less than 50 NTU at 21xc2x0 C.
Microemulsion, as used herein, is a thermodynamically stable isotropic dispersion of oil and water containing domains of nanometer dimensions stabilized by an interfacial film of surface active agent(s). The microemulsions are optically clear because one or more dimensions of the domains is smaller than the wavelength of visible light (approximately 550 nanometers).
There are various types of microemulsions. The microemulsion may be, for example, an oil-in-water (o/w) microemulsion with discrete oil-swollen micelles or oil droplets; a water-in-oil (w/o) microemulsion with discrete water-swollen reversed micelles or water droplets; or a bicontinuous microemulsion. The bicontinuous microemulsion may be, for example, a sponge phase or xe2x80x9cmonolayerxe2x80x9d bicontinuous microemulsion with two nearly equal volume immiscible fluids interlayered by a surfactant monolayer; a normal bicontinuous microemulsion including a water-rich bicontinuous phase with two immiscible fluids interlayered by a xe2x80x9cnormalxe2x80x9d random-oriented lamellar-like surfactant double layers; or a reverse bicontinuous microemulsion including an oil-rich bicontinuous phase with two fluids immiscible interlayered by a xe2x80x9creversedxe2x80x9d random-oriented lamellar-like surfalctant double layers.
Preferred microemulsions form spontaneously and have good stability. The microemulsions are stable preferably for at least a day, more preferably at least 30 days, and most preferably at least 90 days, at room temperature. Stable, as used herein, means that the compositions retain clarity and that there is no visible phase separation within the compositions.
Commercially available silicone polyethers may include a mixture of silicone polyethers. For purposes of this patent application, molecular weight, HLB, PO/EO ratio, and percent silicone of the silicone polyether in the personal care composition means the average molecular weight, HLB, PO/EO ratio, and percent silicone of the silicone polyethers in the composition.
The invention also features a personal care composition in the form of a microemulsion and including water, a volatile silicone, and a silicone polyether having an HLB greater than 4 and selected from the group consisting of AB copolymers, ABA copolymers, graft copolymers, and terpolymers.
When the personal care composition is an antiperspirant, the composition preferably also includes a perspiration reducing effective amount of an antiperspirant salt. The antiperspirant composition may be in the form of an aerosol, pump spray, roll-on, lotion, cream, gel, or stick. The invention also features reducing perspiration from human skin by applying a perspiration reducing effective amount of the antiperspirant composition to the skin.
The invention further features an antiperspirant composition in the form of a microemulsion including water, a volatile silicone, an antiperspirant salt, and a silicone polyether having a molecular weight greater than 1,000.
The invention further features a method of determining the quantities of volatile silicone, silicone polyether, antiperspirant salt, and alcohol that will provide a microemulsion. The method includes dissolving an antiperspirant salt in alcohol to provide an isotropic solution; the solution may also include some water. The isotropic solution then is mixed with varying quantities of volatile silicone and silicone polyether t o provide a plurality (e.g., at least 6, 8, or 12) of mixtures. The phase behavior of the mixtures may be observed to identify those (if any) that are candidates for microemulsion. In addition, the mixtures may further be mixed with varying quantities of an aqueous solution of an antiperspirant salt and the phase behavior of the resultant mixture observed to identify those mixtures (if any) that also are candidates for providing a microemulsion.
Preferably, the quantities of the isotropic solution, volatile silicone, silicone polyether, and/or aqueous salt solution (if present) in the candidates are altered systematically to provide fine-tuned candidates for a microemulsion.